1. Field of the Invention
The present invention relates to a light emitting diode (LED) package and a fabrication method thereof, and more particularly, to an LED package which is superior in heat discharge quality, and compact in size, appropriate for mass production, and to a fabrication method thereof.
2. Description of the Related Art
Recently, a light emitting diode (LED) using a compound of semiconductor material such as GaAs, AlGaAs, GaN, and AlGaInP has been developed to realize diverse colors of light source. The factors contributing to the characteristics of LED products include color, luminance, and light-conversion efficiency. The characteristics of an LED product are influenced by the primary factors including the compound and structure of semiconductor material used in the LED, and also greatly by the secondary factors including package structure for mounting the LED. In order to obtain light-emitting effects appropriate for the user needs, not only the primary factors such as material and structure of the LED, but also the secondary factors such as the structure and material of the LED package need to be improved as well.
In general, in order to use an LED chip for illumination, a high output of light needs to be generated, with light-conversion efficiency of 100 lm/W or more. Since the LED chip is driven with high input power, more than 70% of input power is converted into heat. Therefore, the operation of the LED generates much heat, which needs to be discharged. If the heat is not sufficiently discharged, the temperature of the LED increases, rapidly diminishing the light-conversion efficiency. Therefore, there have been efforts to effectively discharge the heat generated from the LED in a high-output LED package. In order to improve the heat discharge quality of the LED package, Japanese Laid-Open Patent Application No. 2003-218398 discloses techniques of using a separated metal substrate with a narrow slit for an LED package substrate.
In addition, with the current trend of miniaturization and light weight of electronic components, there has been an increasing demand for a very thin, compact size LED package. For example, the LED package used in the backlight unit of the LCD or the camera flash needs to be manufactured in compact size, which in turn, miniaturizes the backlight unit or camera flash. However, the conventional LED packages have not satisfied such needs described above, and also the manufacturing process is complicated.
FIG. 1 is a sectional view illustrating an overall structure of a conventional LED package 10. This LED package 10 uses air as the medium of light. Referring to FIG. 1, the LED package 10 includes a metal substrate 2 with a narrow slit 6, a spacer 4 made of insulating substrate, and a cover plate 9 made of transparent glass. The slit is filled with insulator 3 such as epoxy resin, so that the metal substrate 4 forms two electrodes 2a and 2b that are separated from each other. The metal substrate 2, the spacer 4, and the cover plate 9 are adhered to each other by adhesive sheets 5 and 8 interpositioned between them. In the center of the spacer 4, a cavity or a through hole 4b is formed, and an LED chip 7 is received in the through hole 4b. The side surface of the through hole 4b is coated with a metal film 11. This metal film 11 functions as a reflective surface on which the LED light emitted to the side is reflected upward. The LED 7 is flip-chip bonded to the two electrodes 2a and 2b of the metal substrate 2 via bumps 7a and 7b. The gap between the LED 7 and the metal substrate 2 may be filled with underfill resin.
The LED package 10 uses a metal substrate 2 to enhance the discharge quality of the heat generated from the LED 7. However, in order to manufacture the conventional LED package with the above construction, the metal substrate 2 needs to be finely processed to divide the metal substrate 2 in parts by a narrow slit 6. Therefore, the fabrication process of the LED package 10 is not easy, hindering obtainment of a sufficiently thin, compact size package. Furthermore, it is difficult to flip-chip bond the LED chip 7 precisely on the two electrodes 2a and 2b such that the LED chip 7 is positioned between the two bumps 7a and 7b. 